1. Field of the Invention
The present invention relates to a substrate-processing apparatus using a vacuum load-lock system and a substrate-transferring apparatus. The invention further relates to a buffer mechanism for buffering semiconductor substrates.
2. Description of the Related Art
Generally, chambers of a semiconductor-processing apparatus using a vacuum load-lock system, which is used for manufacturing conventional semiconductor integrated circuits, comprise a load-lock chamber, a transfer chamber and multiple reactors (process chambers) connected to the transfer chamber. For each chamber, a wafer transfer robot is used for supplying wafers automatically. The semiconductor-processing apparatus using a vacuum load-lock system operates in the following manner: First, an atmospheric robot carries a wafer from a cassette or a front opening unified pod (“FOUP”, e.g., a box possessing detachable cassettes and a front opening interface) into a load-lock chamber. After evacuating air from the load-lock chamber, the wafer is transferred to each reactor by a vacuum robot provided inside a common polygonal transfer chamber. Wafers for which processing in the reactor is finished, are transferred into the load-lock chamber by the vacuum robot. Finally, after inside the load-lock chamber is restored to atmospheric pressure, processed wafers are transferred to the cassette or the FOUP by an atmospheric robot. Such apparatuses are generally called “cluster tools”.
Conventionally, cluster tools have a single-wafer-processing type and a batch wafer-processing type. The single-wafer-processing type is a type in which a single wafer is processed by each reactor. The batch wafer-processing type is a type in which multiple wafers are processed by a single reactor.
With the batch wafer-processing type, productivity is high because multiple wafers are processed by a single reactor. In batch processing, the occurrence of non-uniformity of film thickness and film quality of a thin film formed on a wafer frequently becomes a problem. To improve uniformity of film thickness and film quality, using a single-wafer-processing type wafer processing apparatus is effective.
Problems that the invention can resolve are as follows:
In order to increase productivity using a conventional single-wafer-processing type processing apparatus, the number of reactors increases, a footprint (apparatus space required) and a faceprint (the panel width of a apparatus front) increase, and costs run up. This is because the apparatus has a common polygonal transfer room and reactors are attached to it radially. Additionally, due to the increase in the number of reactors, output significantly drops if operation discontinues due to apparatus breakdowns or maintenance.
Furthermore, in the thin film deposition process, it is often the case that process time is short and the processes are performed consecutively. For these reasons, if keeping the next wafer standing by inside a load-lock chamber, a wafer transferring mechanism needs to have double arms. If equipping the wafer transferring mechanism with the double arms, the transferring mechanism complexifies and costs run up. Additionally, the capacity of the load-lock chamber increases, hence time required for evacuating air and time required for restoring to atmospheric pressure are lengthened and transfer rate-limiting factors increase. As a result, throughput is restricted.
Furthermore, even in an apparatus using a regular polygonal type transfer chamber, for the purpose of carrying in and out wafers inside the reactor efficiently, although the wafer transferring mechanism having double arms is better, the transferring mechanism complexities and costs run up.